The present invention relates to a pot-shaped rolling piston of a roll bellows-type pneumatic shock absorber whereby a rolling crease of the roll bellows is supported at an outer mantle surface of an annular wall of the rolling piston during a shock absorbing movement.
Rolling pistons are employed in roll bellows-type pneumatic shock absorbers. Roll bellows-type pneumatic shock absorbers are known in a variety of designs and have been successfully employed especially for shock absorbing functions for axles of trucks and buses. The roll bellows, with at least one end thereof, are fastened to the rolling piston whereby the rolling piston is usually made of metal or plastic materials. In an operating mode, the rolling piston is moved inside the roll bellows, so that the roll bellows is inverted and forms a rolling crease, which in return rolls on the outer mantle surface of the rolling piston.
The manufacture and mounting of the rolling piston requires a great technical expenditure. The rolling piston increases the total weight of the roll bellows-type pneumatic shock absorber. Endeavors to reduce the weight of the roll bellows-type pneumatic shock absorber resulted in the use of lighter materials for the rolling piston and also in different constructive designs.
During a shock absorbing movement the rolling crease exerts a great radial force onto the rolling piston, which when the walls are rather thin, may result in breakage of the rolling piston. Therefore, it has been suggested to provide the walls of the rolling piston with inner reinforcement ribs. The static and dynamic stiffness of the rolling piston then results from a combination of the wall thickness, the reinforcement ribs, and, in a few embodiments, a central supporting body.
Endeavors in the field are still directed towards the reduction of production costs of roll bellow-type pneumatic shock absorbers as well as reduction of the total weight due to selection of less expensive materials. It is also desired to improve the shock absorbing properties, especially by reducing the weight of the unsprung mass.
A rolling piston made from metal, rubber or plastic, is known from the German publication DE-AS 11 27 729 whereby the outer contours of the rolling piston widen in the direction of a bottom section in a continuous manner. The inside of the rolling piston is provided with horizontally arranged chambers that may be pressurized independent from one another. Due to the varying pressurization of the chambers the effective surface of the roll bellows-type pneumatic shock absorber may be adjusted to various operational requirements.
A cylindrical rolling piston is known from DE-AS 12 85 792 whereby the interior in the bottom section is sealed to the outside and is connected via an opening in the horizontal top section to the interior of the roll bellows in a pressure transmitting connection.
Experiments carried out in the past have shown, that the rolling piston, when made from lighter materials and/or provided with a reduced wall thickness, has a reduced stiffness of the walls and thus cannot withstand the maximum loads that occur during operation. The area of the rolling piston wall at which the rolling crease of the roll bellows during a shock absorbing movement is supported, experiences deformations and breakage.
It is known from DE-GM 89 03 264 to provide a rolling piston having a reduced weight and reduced material costs by decreasing the wall thickness of the rolling piston and compensating for the decreased thickness by generating pressure in the interior of the rolling piston.
It is therefore an object of the present invention to provide a light-weight rolling piston having a high stiffness.